Gear indexing gone wrong

[timbrox]

I find it helps to use a pair of pliers to pull the cable through - you need to make sure that there is sufficient tension in the cable so that when you click there is no slack taken in before the shifter moves.

A good way to check if this is the case is once you've got it fully indexed and the shifter in the smallest sprocket if you pull on the exposed cable after it comes out of the barrel adjuster towards where it clamps there should be zero slack in there. If there is even the slightest amount of give then you need to wind the adjuster out until the slack is removed. If this takes more than a couple of full turns then you will have trouble indexing properly so wind it back in again and then loosen and reattach the cable properly.

If it's your first time doing this it may take a couple of tries to get it right so don't get disheartened.

I think this is on the money. There seems to be a lot of slack in the cable. I've tried pulling it through as much as possible, holding with pliers while tightening, but still it remains slack. Any other tips for removing slack in the cable?

 

[weareHKR]

With the cable disconnected from the derailleur.
Ask someone to hold the end of outer cable whilst pulling the inner cable taut, you can then click the shifter & cycle it through however many clicks it's got, you should see/feel the cable moving out with each click, then see it moving back in again whilst you shift through the clicks again.
If it's working ok then re-attach it to the derailleur whilst keeping the inner cable taut, then there cannot be any slack in the cable!
Alternatively, if you can't sort it with the youtube help & all the help in here, I suggest you take it to your local LBS!